Main Subjects : Geophysics

Reservoir Characterization of the Middle Cretaceous Mishrif Formation in the Buzurgan Oilfield, Southern Iraq

Muneef Mohammed; Hameed Salih; Kadhim Mnaty

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 2, Pages 63-77
DOI: 10.33899/earth.2021.170388

The Mishrif Formation is considered the main oil reservoir in the Buzurgan oilfield, southern Iraq. This study aims to characterize and evaluate the reservoir properties of the Mishrif Formation based on the interpretation of well logs data. The logs data for six wells have been analyzed and interpreted by using Techlog 2015.3 software. The lithology of the Mishrif Formation was determined by using the M-N cross plot method based on the interpretation of density, neutron, and sonic logs. The results showed that the Mishrif Formation is mainly composed of limestone. The shale volume in the Mishrif Formation has been estimated from the gamma-ray log. The results illustrated that the shale volume is about 20% of the bulk volume, and may increase to reach the highest value at the upper part of the MA unit of the formation. The porosity of the Mishrif Formation was calculated based on the interpretation of neutron, density, and sonic logs. To achieve accurate values of porosity, the log-derived porosity has been correlated with the core-derived porosity, and the comparison showed a good correlation between the two types of porosity. The results showed that the Mishrif Formation is characterized by low to medium porosity (about 5% to 18%). The secondary porosity of the formation is most dominant in the MB21 unit compared with the other stratigraphic units of the Mishrif Formations. This indicates that the MB21 unit was affected by the diagenesis processes. The MB21 unit of the Mishrif Formation represents the most dominant reservoir because it was delineated by high effective porosity and high oil saturation.

The Study of Lithology by Using the Cross-Section Profiles of The Logs of Shiranish and Mushorah Formations in Ain Zalah and Butmah Fields, Northwestern Iraq

Faris Hassan; Wissam Mohamed; Wafaa Yunus; Abdul-Salam Salih

Iraqi National Journal of Earth Science, 2021, Volume 21, Issue 1, Pages 17-26
DOI: 10.33899/earth.2020.170378

This study deals with the determination of lithology in the Shiranish and Mushorah Formations in wells (Az-24, Az-29, and But-15). The graphical representation of the neutron porosity log (NØ) and the bulk density ρ)b(, shows that the Shiranish (Late Campanian – Early Maastrichtian) and Mushorah (Early Campanian) Formations consist of limestone and dolomite, as well as shale. The proportion of dolomite and chert increases at the expense ofcalcite in the Mushorah Formation. Also, the graphical representation results of the M-N profile for each well indicate that the limestone of the Mushorah Formation were affected by the dolomitization with the development of secondary porosity. Moreover, the limestones were suffered silicification in the form of chert nodules. The MID profile, used in this study to determine the mineralogy gives better and more precise results than that of the M-N profile. The results showed that the dominant minerals are calcite in the Shiranish Formation while dolomite and quartz in the Mushorah Formation, regardless of the gas effects within the studied wells.

Analyzing sensitivity and resolution of some electrical resistivity configurations for detecting subsurface cavities using inverted synthetic models by 2D electrical resistivity tomography technique

Zainab Shanshal; Ahmed Al-Heety

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 2, Pages 64-85
DOI: 10.33899/earth.2020.170370

It is important to determine the location, depth and shape (dimensions) of cavities under subsurface in site investigation phase before construction. This study aims to make a study for properties, analysis and comparison of the results of different electrodes configurations that used in 2-D electrical resistivity Tomography surveys to detection subsurface cavities to determining the appropriate and suitable configurations type that must be conduct in the field to obtain best and accurate results. Two-dimensional synthetic models were created for Geoelectrical resistivity of five different geological features, which reflects the common cases of cavities in nature. These models are (narrow, broad, shallow and deep) cavities adding to one model for multiple cavities.  RES2DMOD program was used to create these models, while RES2DINV program used in Inversion method to obtain the true 2-D inverted resistivity sections for six configuration types of electrode array for 2D electrical resistivity technique, after adding a Gaussian noise ratio of (5%). Generally, we are noticed the possibilities of most tested configuration types for determine electrical anomalies, because the high contrast between the cavities and the surrounding rocks resistivities values. In addition, RMS ratio overall does not exceed 5%, hence, this ratio is an acceptable and indicates to the quality of the inverse process. The Wenner array have high sensitivity to vertical resistivity variations, and Dipole-dipole array have high sensitivity to lateral resistivity variations. While the Schlumberger-wenner have high sensitivity in both lateral and vertical resistivity variations Also, it was noted that the efficiency of all types decreasing with increasing depth of cavities detecting, due to the low percentage of contrast between the cavities and the surrounding rocks. The Wenner beta (WB) configuration is the best choice in terms of inversing true resistivity values, Secondly the Pole-Dipole (PD). While in term of determining the location and shape (approximately dimensions) of cavities, Dipole-Dipole (DD), Wenner-Schlumberger (WS), Wenner Alpha (WA), Dipole-Pole (DP) respectively. However, in case of noisy areas, Wenner Alpha (WA) configuration gives the best result.

Study of the Quaternary Deposits at the East and West Shoulders of Mosul Dam Using Azimuthal 2D Resistivity Imaging

Mahmood Al-Fadhel; Marwan Mutib

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 2, Pages 1-17
DOI: 10.33899/earth.2020.170353

The field survey included three geoelectric traverses on the eastern side of the Tigris River parallel and perpendicular on the axis of the Tairah anticline consisting of seven sites of ( Azimuthal Resistivity Tomography; ART) located above the Quaternary depositions in the southern flank. Two traverses  were also conducted in the western side of the river parallel and perpendicular on the east Butmah anticline consisting of four sites located above the recent sediments in the southern flank of it. The sites are chosen taking into account the consideration of the geological, tectonic and topographic data of previous studies and current field reconnaissance trips.
A sympathetic analysis of the resistivity tomography is performed in nine azimuths of the above mentioned locations using fifteen repetitive processing attempts and the mean root squares ranged between 5.8% -11.7%. The eastern side of the study area with different directions indicates electrical horizons, the first reflects a variable resistivity which represents accumulations of top soil, the second band of high resistivity which reflects the river terraces constitutes, while the third horizon represents the clear extension of the mud and limestone deposits of Fatha Formation with a vertical conductive zones in the rock layers at some traverses. As well as the ART on the western side of the study region identified three electric horizons: the first with high resistivity reflecting the surface soil layer, and the second domain of low resistivity representing the sediments of the valley slopes and concentrating on the southern limb of Butmah anticline. The third of heterogeneous resistivity values reflects  Fatha Formation deposits covering its exposures at the core of the two anticlines and locating beneath the research traverses.
Using the technology of 2D resistivity imaging reveals that the nine orientations around a central point in eleven locations above recent sediments are represented by river terraces and alluvial deposits on the shoulders of the Mosul Dam. The current study concludes the ability to capture fractures, which is of great importance due to their effect on the displacements of the dam's body and Fatha sediments surrounding it.

New Azimuthal Resistance Techniques in the Study of Fractures of the Recent Deposition for Selected Sites near Mosul Dam

Mahmood Al-Fadhel; Marwan Mutib

Iraqi National Journal of Earth Science, 2020, Volume 20, Issue 1, Pages 127-146
DOI: 10.33899/earth.2020.170351

The present study involves applying a new system by picking the apparent resistivity values ​​ from the pseudo-tomography at seven depth's levels and nine orientations with an angle of 20 ° around the mid central point of a 200 m array lengths. The system, which is called the Azimuth Mutib and Al-Fadhel System (AMAS), consists of three types of the electrode arrangement patterns, the first is the Azimuthal Radial Resistance Technique (ARRT) for measurements of resistivity (ρD1 & ρD2), the second is the Azimuthal Forward Resistance Technique (AFRT) for measurements of resistivity (ρD0 & ρD2), and the third is the Backward Resistance Technique (ABRT) for measurements of resistivity (ρD0 & ρD1).
A new mechanism is used in this study that includes a series of calibration steps of the electrode spacing intervals with the apparent depth’s levels and median of the depth of investigation, due to the inability of picking the resistivity values of the true depth's levels from electrical resistivity imaging because there is a wide spectral gradient range of colors. As well, the absence of correlating the values ​​of the depth's levels with the electrode spacing in the RES2DINV software. Accordingly, three values were determined for the missing apparent depth's levels with confirmation of the accordant values of the eight levels of the tomography.
The data of the ART are represented using radial, forward and backward techniques at four sites using polar graphs and Cartesian curves. According to the mechanisms used in global and local studies and researches, the results are analyzed and for determining the values ​​and trends of the electrical anisotropy for Quaternary deposits and the upperlayers of Fatha Formation in the present study area.
The study displays a notable success in applying AMAS by matching between its three mechanisms and deduced the presence of six directions for the strikes of tension and shear fractures (primary and secondary) at two sites near the Mosul Dam penetrating fluvial and alluvial deposits of the Quaternary age.

New Petrophysical Equations for Hartha-Tannuma Interval in the East Baghdad Oil Field

Maan Al-majid

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 2, Pages 136-152
DOI: 10.33899/earth.2019.170285

This study deals with empirical equations linking density and porosity with depth. The density and porosity information were taken from five well logs distributed in the East Baghdad oil field. New empirical equations (porosity - depth, density - depth) for two geological formations (Harta and Sa'di) within Hartha- Tannuma period were produced. The correlation coefficient (R) of these equations ranged from -0.37 to 0.68, which was attributed to variability in lithology and compaction. The depth data of (133) points suited at seismic lines grid scattered in the field were used for applying the new equations. After the new empirical equations that are applied on the whole field, porosity and density contour maps for the period (Hartha- Tannuma) and the two formations (Hartha and Sa'di) were plotted. The high porosity zones were identified, are related to the compaction and petroleum distribution in the field.

Resistivity Isotropicity and Homogeneity for Sub-base Layer of Selected Roads in Ninevah Governorate, Northern Iraq

Ali Almwaly; Marwan Mutib; Mohammed Taha

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 1, Pages 59-79
DOI: 10.33899/earth.2019.170271

Field surveys of electrical resistance are achieved in order to study the sub-base layer of the under constructive roads where the present study is conducted in six locations (Bardarash, Rovya, Mahalabyia 1 and 2, Al-Gwair and Bashiqa) based on the existence of projects for roads under construction by the Directorate of Roads and Bridges. Furthermore, Azimuthal resistivity survey is applied using Parker-Watson array with an electrode spacing and azimuth depending on road directions. Also a reverse surveys are performed on the same points of sounding.
The resistance ratios (Rd1, Rd2) are then calculated and represented as polar diagrams and cartesian curves. Moreover, analysis relationships are done between the phases, amplitudes, frequencies and their reflections. It is observed from the polar diagrams of the mean resistance values, there is a resistivity variation with the depths and directions of the spread. It is also noticed that there are changes of the Anisotropy Coefficient (AC) values reflecting the effect of the lithofacies contrasts of the sub-base layer belonging to the paving and compacting mechanism underneath the central point of the azimuthal survey. A comparison between AC and Homogeneity Indices (HI) are determined, and the latest values are detected using the standard deviation approach which is thought to reflect the dispersion of measured resistances due to the heterogeneity constitutes.

The Use of the Seismic Refraction Tomography Survey Method and the Multi-Channel Analysis Technique of Surface Waves in the Geotechnical Assessment of the Al-Amal Apartments Site in Kirkuk, Northern Iraq Ali

Ali Al-Nuaiemy; Bashar Al-Juraisy; Mahmood Al-Mafraji

Iraqi National Journal of Earth Science, 2018, Volume 18, Issue 2, Pages 89-104
DOI: 10.33899/earth.2018.159260

The current study conducted a seismic refraction survey using seismic refraction tomography (SRT), and the use of the multi-channel analysis technique of surface waves (MASW) at the site of Al-Amal apartments in Kirkuk Governorate ( northern Iraq) in order to determine the thickness, depth and velocity of the sub-surface layers. Moreover, a geotechnical assessment is measured in addition to determining the characteristics of these layers and specifying the appropriate layer for establishing the project.The data are processed and interpreted by using SeisImager™/SW software to obtain the velocity of longitudinal waves (VP) represented in the form of a seismic tomography section. The velocity of shear waves (VS ) is extracted from the phase velocity of Rayleigh surface waves using MASW method. The 2D seismic tomography sections represent longitudinal velocity (VP) and the depth of the survey lines. It also has been got three one-dimensional sections representing shear waves (VS ) with the depth. The results show the presence of three layers, and through dynamic flexibility parameters are calculated, and two of geotechnical parameters are applied for the three layers based on the seismic velocity of longitudinal, shear and density. According to these geotechnical parameters, the third layer has better geotechnical specifications than the layers above it, which is suitable for the engineering project. .

Rock Magnetic Properties during the Paleocene-Eocene Thermal Maximum (PETM): Records from P/E boundary Sections (Sinjar, Shaqlawa) in Iraq

Ahmed Al-Fattah; Ali Al-Juboury; Imad Ghafor

Iraqi National Journal of Earth Science, 2018, Volume 18, Issue 1, Pages 55-74
DOI: 10.33899/earth.2021.170031

Rock magnetic properties have been investigated across the Paleocene/Eocene
boundary in two distally separate sections of Paleogene marine sedimentary rocks
from Iraq, namely the Sinjar and the Shaqlawa sections. The sediments at the
studied sections belong to the Aaliji and the Kolosh formations respectively, which
were previously examined for their biostratigraphy by the authors using planktonic
and benthonic foraminifera to delineate the Paleocene/Eocene (P/E) transition.
Measured magnetic properties include; bulk magnetic susceptibility, hysteresis
cycles, isothermal remnant magnetization (IRM) acquisition, and thermomagnetic
curves analysis. Rock-magnetic results (i.e. low magnetic coercivity component)
indicate greigite as the main magnetic phase at Aaliji rocks, while a mixture of
magnetite and greigite with high magnetic coercivity has been observed at Kolosh
clastics. Magnetic susceptibility is induced by related to both biogenic minerals
(mainly at Aaliji Formation) and transported terrigenous material sources. Multi
varied magnitude phases of high bulk rock magnetic susceptibility observed in
both formations along PETM lithosomes are attributed to two sources: greigite or
biogenic iron oxides source and increase in terrigenous discharge source as
inferred by anoxic to suboxic iron - sulfate-reducing conditions and lithological
change respectively. Both sources referred to some of environmental conditions
associated with Paleocene - Eocene thermal maximum events such as methane
dissociation, water stratification, enhanced hydrological and weathering cycles.

Geothermal Investigation in the plain Between Sheikh Ibrahim and Atshan anticline southeast of Talafar Northweast of Iraq

Ahmed Saeed; Marwan Mutib

Iraqi National Journal of Earth Science, 2006, Volume 6, Issue 1, Pages 17-32
DOI: 10.33899/earth.2006.41315

Geoelectrical investigations were carried out in the area that located between atshan and sheikh Ibrahim anticline and south west respectively the vertical electric sounding was applied by using the collinear and symmetrical schlumberger array with maximum spacing interval for the current and potential electrodes (840 and 90m. respectively ) the sounding station were located in 64 sites through four traverses trending NE-SW. the field curve were interpreted by the partial matching method and the initial models were adjusted by using KMM program with digital partial matching technique. For electric zones were distinguished, the first one represent the surface soil while the second zone reflect of two lithofacies which belong to the upper member of al fat'ha formation while the fourth zone represent a lateral resistivity contrast which reflect lower member of al fat'ha formation and the unit D of the upper member.
Those lateral variations were explained by the geoelectrical traverses which indicate longitudinal fault. More ever geoelectrical section delinated type of this normal fault with about 90m through and 25 degree dipping